Novel diversity in mitochondrial genomes of deep-sea Pennatulacea (Cnidaria: Anthozoa: Octocorallia)

We present the first documented complete mitogenomes of deep-sea Pennatulacea, representing nine genera and eight families. These include one species each of the deep-sea genera <i>Funiculina, Halipteris</i>, <i>Protoptilum</i> and <i>Distichoptilum</i>, four species each of <i>Umbellula</i> and <i>Pennatula</i>, three species of <i>Kophobelemnon</i> and two species of <i>Anthoptilum</i>, as well as one species of the epi- and mesobenthic genus <i>Virgularia</i>. Seventeen circular genomes ranged from 18,513 bp (<i>Halipteris</i> cf. <i>finmarchica</i>) to 19,171 bp (<i>Distichoptilum gracile</i>) and contained all genes standard to octocoral mitochondrial genomes (14 protein-coding genes, two ribosomal RNA genes and one transfer RNA). We found at least three different gene orders in Pennatulacea: the ancestral gene order, the gene order found in bamboo corals (Family Isididae), and a novel gene order. The mitogenome of one species of <i>Umbellula</i> has a bipartite genome (∼13 kbp and ∼5 kbp), with good evidence that both parts are circular.